This module allows user authentication (and can log authentication
requests) against information stored in a PostgreSQL database.

    * Authentication
        One database, and one (or two) tables.  One table holds the
        username and the encrypted (or plain) password.  The other table
        holds the username and the names of the group to which the user
        belongs.  It is possible to have username, groupname and
        password in the same table.

    * Access Logging
        Every authentication access is logged in the same database of
        the authentication table, but in different table.  User name and
        date of the request are logged.  As option, it can log password,
        ip address, request line.
